Affordable Wind Turbines Vawt™ was developed for both residential use and utility scale projects including entire communities, neighborhoods or agricultural groups coming together on a project basis to generate power. The rooftop or pole mounted Affordable Wind Turbines Vawt™ is an affordable, quiet and powerful, bird safe, scalable wind turbine system.

Scalability: You can start with one Affordable Wind Turbines Vawt turbine and add more turbines per pole, and more poles as your power needs grow- without the cost, time or materials waste of major construction. We call multiple Affordable Wind Turbines Vawt configurations WindOrchards. Locally, the benefits would be the capability to easily generate power and have off-grid emergency power for any neighborhood.

Because of the unique wind turbulence smoothing capability of the blades, the Affordable Wind Turbines Vawt is an ‘urban tolerant’ wind turbine.

Affordable Wind Turbines Vawt can be retrofit to any utility pole, unused utility poles, or retrofit to other wind turbine poles.

Availability is critical to our business model. Once in production we will have the capability to manufacture several thousand turbines a month from one manufacturing operation. Future goals include expanding manufacturing of the Affordable Wind Turbines Vawt worldwide, especially in areas of critical need of economic development and energy. Affordable Wind Turbines Vawt Company Mission The Affordable Wind Turbines Vawt Philosophy The Affordable Wind Turbines Vawt Promise Testing The Affordable Wind Turbines Vawt, Features:

Captures a higher amount of potential wind energy per diameter of swept area Operates at slower RPM with higher load-to-torque conversion for harnessing a broader range of wind velocities. Made of durable, ultra-light materials which have established outdoor lifespans in excess of 25 years. Silent operation with little or no vibrations. Shape is easily visible and non-Lethal to birds. Higher aesthetic design value for public areas. Lightweight materials that lower shipping costs substantially. Self-Directing Blade design that allows energy production in turbulent wind conditions. Easy installation that requires no significant changes to existing support structures. Easily Affordable

A wind turbine is a popular name for a device that converts kinetic energy from the wind into electrical power . Technically there is no turbine used in the design but the term appears to have migrated from parallel hydroelectric technology. The correct description for this type of machine would be aerofoil-powered generator .

The result of over a millennium of windmill development and modern engineering, today's wind turbines are manufactured in a wide range of vertical and horizontal axis types. The smallest turbines are used for applications such as battery charging for auxiliary power for boats or caravans or to power traffic warning signs. Slightly larger turbines can be used for making contributions to a domestic power supply while selling unused power back to the utility supplier via the electrical grid . Arrays of large turbines, known as wind farms , are becoming an increasingly important source of renewable energy and are used by many countries as part of a strategy to reduce their reliance on fossil fuels .

History

Windmills were used in Persia (present-day Iran) as early as 200 B.C. [ 1 ] The windwheel of Hero of Alexandria marks one of the first known instances of wind powering a machine in history. [ 2 ] [ 3 ] However, the first known practical windmills were built in Sistan , an Eastern province of Iran, from the 7th century. These " Panemone " were vertical axle windmills, which had long vertical drive shafts with rectangular blades. [ 4 ] Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind grain or draw up water, and were used in the gristmilling and sugarcane industries. [ 5 ]

Windmills first appeared in Europe during the Middle Ages . The first historical records of their use in England date to the 11th or 12th centuries and there are reports of German crusaders taking their windmill-making skills to Syria around 1190. [ 6 ] By the 14th century, Dutch windmills were in use to drain areas of the Rhine delta.

The first electricity-generating wind turbine was a battery charging machine installed in July 1887 by Scottish academic James Blyth to light his holiday home in Marykirk , Scotland. [ 7 ] Some months later American inventor Charles F. Brush built the first automatically operated wind turbine for electricity production in Cleveland, Ohio . [ 7 ] Although Blyth's turbine was considered uneconomical in the United Kingdom [ 7 ] electricity generation by wind turbines was more cost effective in countries with widely scattered populations. [ 6 ]

In Denmark by 1900, there were about 2500 windmills for mechanical loads such as pumps and mills, producing an estimated combined peak power of about 30 MW. The largest machines were on 24-meter (79 ft) towers with four-bladed 23-meter (75 ft) diameter rotors. By 1908 there were 72 wind-driven electric generators operating in the United States from 5 kW to 25 kW. Around the time of World War I, American windmill makers were producing 100,000 farm windmills each year, mostly for water-pumping. [ 9 ]

By the 1930s, wind generators for electricity were common on farms, mostly in the United States where distribution systems had not yet been installed. In this period, high-tensile steel was cheap, and the generators were placed atop prefabricated open steel lattice towers.

A forerunner of modern horizontal-axis wind generators was in service at Yalta , USSR in 1931. This was a 100 kW generator on a 30-meter (98 ft) tower, connected to the local 6.3 kV distribution system. It was reported to have an annual capacity factor of 32 percent, not much different from current wind machines. [ 10 ]

In the autumn of 1941, the first megawatt-class wind turbine was synchronized to a utility grid in Vermont . The Smith-Putnam wind turbine only ran for 1,100 hours before suffering a critical failure. The unit was not repaired, because of shortage of materials during the war.

Despite these diverse developments, developments in fossil fuel systems almost entirely eliminated any wind turbine systems larger than supermicro size. In the early 1970s, however, anti-nuclear protests in Denmark spurred artisan mechanics to develop microturbines of 22 kW. Organizing owners into associations and co-operatives lead to the lobbying of the government and utilities and provided incentives for larger turbines throughout the 1980s and later. Local activists in Germany, nascent turbine manufacturers in Spain, and large investors in the United States in the early 1990s then lobbied for policies that stimulated the industry in those countries. Later companies formed in India and China. As of 2012, Danish company Vestas is the world's biggest wind-turbine manufacturer.

Resources

A quantitative measure of the wind energy available at any location is called the Wind Power Density (WPD). It is a calculation of the mean annual power available per square meter of swept area of a turbine, and is tabulated for different heights above ground. Calculation of wind power density includes the effect of wind velocity and air density. Color-coded maps are prepared for a particular area described, for example, as "Mean Annual Power Density at 50 Metres". In the United States, the results of the above calculation are included in an index developed by the National Renewable Energy Laboratory and referred to as "NREL CLASS". The larger the WPD calculation, the higher it is rated by class. Classes range from Class 1 (200 watts per square meter or less at 50 m altitude) to Class 7 (800 to 2000 watts per square m). Commercial wind farms generally are sited in Class 3 or higher areas, although isolated points in an otherwise Class 1 area may be practical to exploit. [ 12 ]

Wind turbines are classified by the wind speed they are designed for, from class I to class IV, with A or B referring to the turbulence. [ 13 ]

Class

Avg Wind Speed (m/s)

Turbulence

IA

10

18%

IB

10

16%

IIA

8.5

18%

IIB

8.5

16%

IIIA

7.5

18%

IIIB

7.5

16%

IVA

6

18%

IVB

6

16%

Efficiency

Not all the energy of blowing wind can be harvested, since conservation of mass requires that as much mass of air exits the turbine as enters it. Betz's law gives the maximal achievable extraction of wind power by a wind turbine as 59% of the total kinetic energy of the air flowing through the turbine. [ 14 ]

Further inefficiencies, such as rotor blade friction and drag , gearbox losses, generator and converter losses, reduce the power delivered by a wind turbine. Commercial utility-connected turbines deliver 75% to 80% of the Betz limit of power extractable from the wind, at rated operating speed. [ 15 ] [ 16 ]

Efficiency can decrease slightly over time due to wear. Analysis of 3128 wind turbines older than 10 years in Denmark showed that half of the turbines had no decrease, while the other half saw a production decrease of 1.2% per year. [ 17 ]

Types

The three primary types: VAWT Savonius, HAWT towered; VAWT Darrieus as they appear in operation

Wind turbines can rotate about either a horizontal or a vertical axis, the former being both older and more common. [ 18 ]

Horizontal axis

Components of a horizontal axis wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position

Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane , while large turbines generally use a wind sensor coupled with a servo motor . Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator. [ 19 ]

Since a tower produces turbulence behind it, the turbine is usually positioned upwind of its supporting tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted forward into the wind a small amount.

Downwind machines have been built, despite the problem of turbulence (mast wake), because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since cyclical (that is repetitive) turbulence may lead to fatigue failures, most HAWTs are of upwind design.

Turbines used in wind farms for commercial production of electric power are usually three-bladed and pointed into the wind by computer-controlled motors. These have high tip speeds of over 320 km/h (200 mph), high efficiency, and low torque ripple, which contribute to good reliability. The blades are usually colored white for daytime visibility by aircraft and range in length from 20 to 40 meters (66 to 131 ft) or more. The tubular steel towers range from 60 to 90 meters (200 to 300 ft) tall. The blades rotate at 10 to 22 revolutions per minute. At 22 rotations per minute the tip speed exceeds 90 meters per second (300 ft/s). [ 20 ] [ 21 ] A gear box is commonly used for stepping up the speed of the generator, although designs may also use direct drive of an annular generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with protective features to avoid damage at high wind speeds, by feathering the blades into the wind which ceases their rotation, supplemented by brakes .

Vertical axis design

A vertical axis Twisted Savonius type turbine.

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable. It is also an advantage when the turbine is integrated into a building because it is inherently less steerable. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance.

The key disadvantages include the relatively low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient , the 360 degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade, the pulsating torque generated by some rotor designs on the drive train, and the difficulty of modelling the wind flow accurately and hence the challenges of analysing and designing the rotor prior to fabricating a prototype. [ 22 ]

When a turbine is mounted on a rooftop the building generally redirects wind over the roof and this can double the wind speed at the turbine. If the height of a rooftop mounted turbine tower is approximately 50% of the building height it is near the optimum for maximum wind energy and minimum wind turbulence. Wind speeds within the built environment are generally much lower than at exposed rural sites, [ 23 ] [ 24 ] noise may be a concern and an existing structure may not adequately resist the additional stress.

"Eggbeater" turbines, or Darrieus turbines, were named after the French inventor, Georges Darrieus. [ 25 ] They have good efficiency, but produce large torque ripple and cyclical stress on the tower, which contributes to poor reliability. They also generally require some external power source, or an additional Savonius rotor to start turning, because the starting torque is very low. The torque ripple is reduced by using three or more blades which results in greater solidity of the rotor. Solidity is measured by blade area divided by the rotor area. Newer Darrieus type turbines are not held up by guy-wires but have an external superstructure connected to the top bearing. [ 26 ]

A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety has variable pitch to reduce the torque pulsation and is self-starting. [ 27 ] The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades may be used. [ 28 ]

These are drag-type devices with two (or more) scoops that are used in anemometers, Flettner vents (commonly seen on bus and van roofs), and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops.

Twisted Savonius

Twisted Savonius is a modified savonius, with long helical scoops to provide smooth torque. This is often used as a rooftop windturbine and has even been adapted for ships . [ 29 ]

Another type of vertical axis is the Parallel turbine, which is similar to the crossflow fan or centrifugal fan. It uses the ground effect . Vertical axis turbines of this type have been tried for many years: a unit producing 10 kW was built by Israeli wind pioneer Bruce Brill in the 1980s. [ 30 ] [ unreliable source? ]

Unconventional designs

One E-66 wind turbine at Windpark Holtriem , Germany, carries an observation deck, open for visitors. Another turbine of the same type, with an observation deck, is located in Swaffham , England. Airborne wind turbines have been investigated many times but have yet to produce significant energy. Conceptually, wind turbines may also be used in conjunction with a large vertical solar updraft tower to extract the energy due to air heated by the sun.

The ram air turbine is a specialist form of small turbine that is fitted to some aircraft. When deployed, the RAT is spun by the airstream going past the aircraft and can provide power for the most essential systems if there is a loss of all on–board electrical power. [ citation needed ]

Wind turbines on public display

A few localities have exploited the attention-getting nature of wind turbines by placing them on public display, either with visitor centers around their bases, or with viewing areas farther away. [ 41 ] The wind turbines are generally of conventional horizontal-axis, three-bladed design, and generate power to feed electrical grids, but they also serve the unconventional roles of technology demonstration, public relations, and education.

Small wind turbines

A small Quietrevolution QR5 Gorlov type vertical axis wind turbine in Bristol, England. Measuring 3 m in diameter and 5 m high, it has a nameplate rating of 6.5 kW to the grid.

Small wind turbines may be used for a variety of applications including on- or off-grid residences, telecom towers, offshore platforms, rural schools and clinics, remote monitoring and other purposes that require energy where there is no electric grid, or where the grid is unstable. Small wind turbines may be as small as a fifty-watt generator for boat or caravan use. Hybrid solar and wind powered units are increasingly being used for traffic signage, particularly in rural locations, as they avoid the need to lay long cables from the nearest mains connection point. [ 42 ] The U.S. Department of Energy's National Renewable Energy Laboratory (NREL) defines small wind turbines as those smaller than or equal to 100 kilowatts. [ 43 ] Small units often have direct drive generators, direct current output, aeroelastic blades, lifetime bearings and use a vane to point into the wind.

Larger, more costly turbines generally have geared power trains, alternating current output, flaps and are actively pointed into the wind. Direct drive generators and aeroelastic blades for large wind turbines are being researched.

Wind turbine spacing

On most horizontal windturbine farms, a spacing of about 6-10 times the rotor diameter is often upheld. However, for large wind farms distances of about 15 rotor diameters should be more economically optimal, taking into account typical wind turbine and land costs. This conclusion has been reached by research [ 44 ] conducted by Charles Meneveau of the Johns Hopkins University, [ 45 ] and Johan Meyers of Leuven University in Belgium, based on computer simulations [ 46 ] that take into account the detailed interactions among wind turbines (wakes) as well as with the entire turbulent atmospheric boundary layer. Moreover, recent research by John Dabiri of Caltech suggests that vertical wind turbines may be placed much more closely together so long as an alternating pattern of rotation is created allowing blades of neighbouring turbines to move in the same direction as they approach one another. [ 47 ]

Health monitoring of wind turbines

Due to data transmission problems, health monitoring of wind turbines is usually performed using several accelerometers and strain gages attached to the nacelle to monitor the gearbox and equipments. Recently, digital image correlation and stereophotogrammetry are used to measure dynamics of wind turbine blades. These methods usually measure displacement and strain to identify location of defects. Dynamic characteristics of non-rotating wind turbines have been measured using digital image correlation and photogrammetry. [ 48 ] Three dimensional point tracking has also been used to measure rotating dynamics of wind turbines. [ 49 ]

Records

The Vestas V164 has a rated capacity of 8.0 MW, [ 50 ] has an overall height of 220 m (722 ft), a diameter of 164 m (538 ft), and is the world's largest-capacity wind turbine since its introduction in 2014. At least five companies are working on the development of a 10 MW turbine.

Largest swept area

The turbine with the largest swept area is the Samsung S7.0-171, with a diameter of 171 m, giving a total sweep of 22966 m 2 .

Four turbines at Rønland wind farm in Denmark share the record for the most productive wind turbines, with each having generated 63.2 GWh by June 2010. [ 61 ]

Highest-situated

Since 2013 the world's highest-situated wind turbine was made and installed by WindAid and is located at the base of the Pastoruri Glacier in Peru at 4,877 meters (16,001 ft) above sea level. [ 62 ] The site uses the WindAid 2.5 kW wind generator to supply power to a small rural community of micro entrepreneurs who cater to the tourists who come to the Pastoruri glacier. [ 63 ]